Iron(II) Complexes of a Potentially Quinquedentate Macrocyclic Ligand having an 'N3S2' Donor Set and the Crystal and Molecular Structures of a High-spin (S = 2) Complex and a Low-spin (S = 0) Complex

DOI: 10.1039/DT9810001965

Source and publish data:

Journal of the Chemical Society, Dalton Transactions p. 1965 - 1972 (1981)

Update date:2022-08-04

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Authors:

Cairns, Colin

Nelson, S. Martin

Drew, Michael G. B.

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Article abstract of DOI:10.1039/DT9810001965

A series of iron(II) complexes of the 17-membered macrocyclic ligand L, having an 'N3S2' donor set, derived from the Schiff-base condensation of 2,6-diacetylpyridine with 4,7-dithiadecane-1,10-diamine, are described.Physical measurements (magnetic, Moessbauer) characterise the complexes as high-spin (S = 2) and low-spin (S = 0) depending on the nature of the associated unidentate ligands (halide, NCS(1-), MeOH, MeCN, pyridine, or NH3).Single-crystal X-ray structure determinations of two of the complexes reveal a versatility in the conformations and co-ordination modes of the macrocycle.Crystals of the low-spin complex (1) are monoclinic with a = 31.640(8), b = 11.019(8), c = 11.155(7) Angstroem, β = 96.40(3) deg., Z = 4, and space group P2₁/a.Crystals of the high-spin complex (2) are monoclinic with a = 18.512(11), b = 18.279(12), c = 8.125(9) Angstroem, β = 113.1(2) deg., Z = 4, and space group P2₁/a.The two structures were solved by Patterson and Fourier methods from 2548 and 1772 reflections above background measured by diffractometer and refined by full-matrix least squares to R 0.047 and 0.102 respectively.In both (1) and (2), the co-ordination geometry of the metal ion is distorted octahedral.In (1), the macrocycle adopts a 'wrap-around' conformation to occupy five of the octahedral sites , the sixth being filled by the nitrogen atom of the -NCS group <1.965(9) Angstroem>.In (2), one sulphur atom of the macrocycle is not bonded to the metal while the other is only weakly co-ordinated <2.806(5) Angstroem> cis to the trimethine nitrogens .The remaining two octahedral sites are occupied by the Cl(1-) ion (trans to the pyridine nitrogen) and the oxygen atom of the MeOH molecule .Possible structures for the remaining complexes of the series including three modifications of are considered.